The present invention relates to a chassis with four supporting wheels or more, and with means for height adjustment of these in order to provide adjustment of the orientation of a chassis member in relation to a reference orientation, preferably vertically. Such a chassis is preferably applicable for a portal tractor, but is also applicable in other cross-country vehicles, where it is preferred to maintain a given orientation of chassis, irrespective of roughness or slope in the ground and where a four-point distribution is desired as well. Portal tractors, which are built up as three-wheeled vehicles with stationary members so they follow the slope of the ground, are known. These are intended to be used with row crops with growth in the shape of trees and bushes. Such crops will grow vertically irrespective of slope of the ground. When the known portal tractors are used on sloping ground, they will run against trees as these grow vertically. The three-wheeled construction makes it difficult to drive on the ground, as the centre of gravity must be kept within the triangle of the three wheels; also, optimal working conditions are not present between a tractor driving on sloping ground and trees or other growths growing vertically.
A chassis, with a construction where the wheels are individually adjustable, is also known. These are, however, technically complicated and expensive constructions.
It is the purpose of the present invention to show a chassis of the type mentioned in the beginning, which makes it possible to swing an upper part of the chassis sideways as well as back and forth in the direction of travel for a vehicle, for example a portal tractor, in such a way that a chassis member, for example a portal for supporting tools, can be adjusted to a preferred orientation, preferably vertically, and which at the same time makes a weight distribution on the wheels of the vehicle possible.
According to the present invention this is obtained with a chassis which is peculiar in that it includes two lower side members which at each end are equipped with one or more wheels or caterpillar tracks, that each lower side member between its front end and rear end includes a first bearing with an axis of rotation substantially transversely of the longitudinal direction of the lower side member, that an upper side member is connected to each of these first bearings, and that each upper side member includes two other bearings at an upper part thereof at different distances from the lower side member and with axes of rotation oriented in the longitudinal direction of the lower side members, and that two parallel cross members are connected in pairs to these other bearings for forming a parallelogram connection between the upper side members and the cross members.
A chassis according to the invention, for example for a cross-country portal tractor, can be provided with four driving and/or steering wheels or caterpillar track. The chassis is built up so there is a lower side member between a front wheel and a rear wheel or caterpillar track, and there is such a lower side member at each side of the vehicle. It is most common that the wheels are oriented for driving in the longitudinal direction of the side members; but it is possible to have the wheels oriented for driving transversely to the lower longitudinal direction of the side members.
On the side member there is a horizontal bearing with the axis transversely to the direction of travel, at this bearing an upper side member is mounted, which preferably is a vertical member forming one side of the portal. This makes swinging back and forth in the direction of travel possible.
At the top in the upper side member there are two bearings, which preferably are horizontal bearings with their axis of rotation oriented in the longitudinal direction of the lower side member, i.e. with an orientation longitudinally of the direction of travel.
The opposite side of the chassis is built up in the same way, with lower side member and upper side member, and at an upper part of the upper side members two cross members are disposed, forming a bottom and a top in an articulated parallelogram. The two bearings at the top at each of the upper side members create corners in the articulated parallelogram formed between the upper side members and the cross members. This makes swinging back and forth transversely to direction of driving possible.
According to the invention, a portal tractor with a chassis may advantageously be used for maintenance of Christmas trees and other row cultures on even or broken ground as well as uneven area where other portal tractors cannot run.
A portal tractor according to the invention with a four-point chassis is advantageous by having four-point weight distribution and a regulation of the tilting of the portal in a construction with a technically simple construction based on application of two mutually connected side members, instead of an independent and individual suspension and regulation of each wheel.
The centre of gravity is not so difficult to keep within the four wheels. By means of the structuring of the portal's points of support and the way in which longitudinally adjustable mechanisms, preferably in the shape of hydraulic cylinders, are mounted, it is possible to distribute the weight of the machine on to all four wheels.
If, for example, the right front wheel travels down into a hollow, then the difference between the right side member and the left side member will be distributed with half the deflection of the portal member through the connected hydraulic cylinders.
Portal tractors can be tilted sideways and back and forth in relation to side members/direction of travel. This makes it possible to adjust the portal on the tractor, so it is always vertical. On the portal member tool for the maintenance of for example Christmas trees and other row cultures can be mounted, which creates optimal working conditions for vertical working devices for vertical trees.
According to a specific embodiment, the chassis according to the invention is peculiar in that between a third bearing on a lower cross member and a fourth bearing on an upper cross member, a first longitudinally adjustable mechanism is arranged for extending or reducing the distance between the third and fourth bearing.
According to a further embodiment, the chassis is peculiar in that between a fifth bearing on a lower side member and a sixth bearing on an upper side member, another longitudinally adjustable mechanism is arranged that can extend or reduce the distance between the fifth and sixth bearing. This is particularly anticipated that a double-acting hydraulic cylinder is provided between each lower side member and corresponding upper side member.
With these embodiments it becomes possible to regulate the inclination of a chassis member in a sideways direction and in longitudinal direction, respectively, by extending or shortening it or the relevant mechanisms. This may occur as a result of a signal, for example from an electronic control signal which receives a reference signal from an electronic level, whereby the arrangement of the wheels on a sloping or uneven ground is detected.
According to a further embodiment, the chassis is peculiar in that the two cross members include a seventh bearing and an eighth bearing, respectively, each with an axis of rotation oriented in the longitudinal direction of the lower side members, that between these a central member is arranged; that at one of the cross members a further cross member is arranged about a ninth bearing with an axis of rotation oriented in the longitudinal direction of the lower side members, that at the ends of the further cross member there are tenth bearings with an axis of rotation oriented in the longitudinal direction of the lower side members, that each lower side member comprise an eleventh bearing at a distance from the first bearing and with an axis of rotation oriented transversely to the longitudinal direction of the lower side member, and that at each side a connecting bar is arranged between the tenth and eleventh bearing. With this construction it is possible to create a technically simple chassis where the weight distribution is established by the further cross member swinging about the ninth bearing. The central member can be used for carrying tools and/or for carrying a driver's cab for the vehicle.
Hereby, a chassis member, for example the central member or a side member, can be kept in a preferred orientation, for example vertical, simultaneously with a difference of height between the wheel/side members of the portal frame is distributed by a simple swinging movement without the need to use longitudinally adjustable mechanisms between lower and upper side members.
If the connecting rods are longitudinally adjustable mechanisms that can extend or reduce the distance between the tenth and eleventh bearing, it is possible to regulate the inclination of the chassis member in longitudinal direction by extending or shortening the mechanism.
The shape of a chassis according to the invention is flexible, as it is anticipated that the longitudinally adjustable mechanisms are selected among hydraulic, mechanic, electrically activating actuators, for example single- or double-acting hydraulic cylinders, racks or electrical linear actuators. According to the invention, a chassis can hereby be established for vehicles irrespective of whether these are electrically driven or driven by an internal combustion engine as power source in order to power a hydraulic pump. Thus, it is anticipated that the height adjustment means include a power source such as hydraulic pump, electric motor or the like as well as means for adjusting the orientation of the chassis member and which is connected to a power source in order to activate it for establishing a preferred orientation of the chassis member.
Alternatively, it is possible to use a pneumatic cylinder as longitudinally adjustable mechanisms even though it is preferred to use mechanisms with the possibility of a stationary longitudinal adjustment.
According to a further embodiment, the chassis is peculiar in that in a supply circuit to the hydraulic cylinders, there is inserted a regulating valve or a mechanism with the same function which by means of control signals from the height adjustment means can extend or shorten the hydraulic cylinders. Hereby, it is possible to establish the preferred displacements of the mutual chassis members by means of a control signal, preferably electronic, for setting of the valves, so the preferred extensions/reductions of the used hydraulic cylinders are obtained.
According to the invention, the chassis can have different shapes depending on the application intended. For use as a portal tractor it is anticipated that it forms a largely U-shaped, L-shaped or H-shaped portal for supporting the processing tools in a chassis member for treating vertically oriented crops irrespective of slope of the ground where the crops grow.
Alternatively, the chassis can be used in other vehicles as for example combined harvesters, tractors or contracting machines where it is preferred to maintain part of the vehicle or the chassis in a desired well-defined orientation irrespective of the character or slope of the ground.
In the following, the invention will be explained in more detail with reference to the schematic drawing enclosed, where: